The present invention relates to seat suspension systems for vehicle seats.
Numerous vehicle seat suspensions are known, including those having air bag or air spring suspensions for resiliently supporting a seat in a selected position. In such suspension systems, pressurized air is delivered to or exhausted from the air bag to adjust the elevation of the seat. The use of an air bag permits upward and downward vibrations of the seat. To counteract these vibrations, shock-absorbing cylinders have been used to dampen the seat vibrations.
In one known approach, as the elevation of the seat suspension is changed by inflating or deflating the air bag, the shock absorbing cylinder has a piston supporting rod which extends or retracts, depending upon the direction in which the seat elevation is changed. In this approach, the shock absorbing cylinder is designed to be capable of extension and retraction throughout the entire range of seat elevation adjustment. In addition, these seat suspension systems are understood to use shock absorbing cylinders with pistons that, at a given seat velocity, apply a constant dampening force over the full stroke of the piston. If the dampening force were non-constant for a given seat velocity in such systems, problems would ensue. For example, in such systems a non-constant dampening force in response to a given velocity of seat movement would mean that the ride provided by the seat would vary depending upon the seat elevation.
U.S. Pat. No. 3,951,373 illustrates one form of seat suspension utilizing a shock absorbing cylinder and an air bag or air spring. In this construction, the shock absorber is understood to have a stroke which is capable of extending and retracting throughout the full range of seat height adjustment. However, in this construction, a hand knob may be operated to adjust the throw of a shaft to thereby change the effective length of the shock absorber.
Although numerous seat suspension systems are known, a need nevertheless exists for an improved seat suspension system having new and non-obvious differences over known systems.
In accordance with one embodiment, a seat suspension system may comprise a seat support adapted to support a seat above the floor of a vehicle. The seat support may include a seat supporting member to which the seat is mounted. The seat support and thus the seat supporting member are raisable and lowerable to support the seat at various elevations relative to the floor of the vehicle.
A seat height adjuster is coupled to the seat support and adapted to raise and lower the seat support and thereby any seat supporting member and seat between various elevations and to a selected elevation. Rather than rigidly supporting the seat at the selected elevation, the seat height adjuster typically allows the seat support, and any seat supporting member, and thereby the seat, to move upwardly and downwardly in response to vibrations. As one specific example, the seat height adjuster may comprise an air spring positioned below the seat supporting member and which is operable to raise and lower the seat supporting member to correspondingly adjust the elevation of the seat.
A vibration damper is provided to dampen movements of the seat in response to seat vibrations. In one form, the vibration damper has an upper end portion coupled to the seat supporting member and a lower end portion coupled to the seat support. In this form, the vibration damper includes a dampening cylinder with a dampening piston therein. The dampening piston applies a dampening force to the seat support to dampen seat vibrations. The dampening piston may be biased towards a first or home position, with the vibration dampener being adapted to dampen movements of the dampening piston away from the first position to thereby dampen vibrations of the seat.
In one specific form, the dampening cylinder may be supported for selective movement relative to the floor of the vehicle such that the elevation of the first or home position is adjustable to correspond to adjustments in the selected elevation of the seat. As a specific example, the seat height adjuster and vibration damper may cooperate to adjust the elevation of the first or home position of the dampening piston with each change in the selected elevation by the seat height adjuster. With this approach, it is unnecessary to require the vibration damper to operate over the full range of elevation adjustments permitted by the seat height adjuster. As another aspect of one exemplary seat suspension system, the seat height adjuster and vibration damper may cooperate to automatically and simultaneously adjust the elevation of the first or home position with changes in the selected elevation of the seat. More specifically, the seat height adjuster and vibration damper may be adapted to adjust the elevation of the home position the same amount as the selected seat elevation is adjusted by the seat height adjuster.
The vibration damper may be adapted to apply a dampening force which is greater when the dampening piston is at a first distance from the home position than when the dampening piston is at a second distance from the home position, the second distance being shorter than the first distance. More specifically, at a given velocity of the seat in response to vibration, the dampening force may vary nonlinearly with the distance the dampening piston travels from the first or home position. The dampening force may also be constant over a range of travel from the home position and then increase after the range is exceeded.
The vibration damper may be adapted to selectively relieve the application of the dampening force during raising and lowering of the seat by the seat height adjuster. In addition, the vibration dampener may provide substantially the same dampening force immediately after a height adjustment by the seat height adjuster as the dampening force provided immediately before the seat height adjustment. Consequently, the uniformity of the seat ride is enhanced regardless of the elevation to which the seat has been adjusted. In addition, by relieving the dampening force during raising and lowering of the seat, the dampening force need not be overcome as the seat height is adjusted. Furthermore, the vibration damper may be of a type which biases the seat toward the elevation at which the seat height adjuster has adjusted the seat. The vibration damper may provide a dampening force which varies in response to vibrations. For example, the dampening force may vary nonlinearly with the distance the seat travels from the selected elevation. The vibration damper may be adapted to relieve the application of the dampening force to the seat support during at least certain changes in the elevation of the seat by the seat height adjuster. In one specific approach, the vibration damper does not apply a dampening force during the entire time the elevation of the seat is being changed by the seat height adjuster. Again, the dampening force applied by the vibration damper immediately following a change in seat elevation by the seat height adjuster may be the same as the dampening force applied immediately before any such seat elevation change. Consequently, the seat may provide the same ride regardless of the seat elevation.
More specifically, the seat suspension system may include a latch coupled to the seat support and adapted to latch the seat at a desired elevation when the latch is in a first position. The latch may also be adapted to unlatch the seat to permit seat height adjustment when the latch is in a second position. In this approach, the seat height adjuster raises and lowers the seat support and thereby the seat between first and second elevations relative to the floor of the vehicle when the latch is unlatched. In addition, the seat height adjuster and seat support permit movement of the seat in response to vibrations when the seat is latched at the desired elevation. The vibration damper may comprise a shock absorber with a cylinder housing and a piston within the housing which moves therein to dampen vibrations. In one specific approach, the seat may be shifted by the seat height adjuster when the seat is unlatched without varying the location of the piston within the housing.
In a specific embodiment, a rod is provided and may extend through the cylinder housing. The latch in this specific example is adapted to selectively engage the rod to couple the dampening piston to the seat to dampen seat vibrations. Conversely, the latch disengages the rod to decouple the dampening piston from the seat as the seat elevation is changed by the seat height adjuster. The latch may include one or more gripping elements for selectively engaging and disengaging the rod. To facilitate engagement of the latch to the rod, both the latch and rod may include friction enhanced surfaces which engage one another during coupling of the latch to the rod. These friction enhanced surfaces may comprise a plurality of gripping ridges or teeth.
In another embodiment, the latch may be adapted for coupling to the exterior of a dampening cylinder housing when the latch is in a first or latched position. When latched, the dampening cylinder is coupled to the seat support to apply a dampening force in opposition to seat vibrations. In addition, the latch may be adapted for decoupling from the cylinder housing when the latch is in a second or unlatched position to block the vibration damper from applying a dampening force to the seat. The latch may comprise one or more latch arms pivotably coupled to the seat support and which have a latch surface. The cylinder housing may also support a latch gripping surface. The latch arm is pivoted to shift the latch surface into and out of engagement with the latch gripping surface as the latch is shifted between the first and second positions. The latch and latch gripping surfaces may be friction enhanced surfaces. In an exemplary form, these surfaces include a plurality of ridges or teeth positioned to engage one another when the latch is in the latched or first position. In this embodiment, the vibration dampening cylinder may be coupled to the seat support so as to move with the seat and relative to the latch when the latch is in the second or unlatched position and the elevation of the seat is adjusted by the seat height adjuster.
As a further aspect of one seat suspension embodiment, the vibration damper may be coupled to the air spring so as to control the air spring to return the seat toward a central or home position when the latch is in a latched position and the load on the seat is varied and causes the seat elevation to change outside of a predetermined range. For example, the seat height adjuster may adjust or set the elevation of the seat between a lower-most elevation and an upper-most elevation. The vibration damper may limit vibrations of the seat to a dampening range from a first upper extreme to a second lower extreme. Thus, the seat may move upwardly from the elevation set by the seat height adjuster to the upper extreme and downwardly from the set elevation to the lower extreme. The distance between the first upper extreme and second lower extreme in this exemplary seat suspension is smaller than the distance through which the elevation of the seat is adjustable by the seat height adjuster. Also, the motion permitted in response to vibrations may be asymmetric relative to the set elevation, for example a greater travel being permitted in compression than in extension. The vibration damper may include a central or home position between the first and second extremes of motion, with the vibration damper biasing the seat to the home position when the latch is in a first or latched position.
In addition, the vibration damper may be coupled to the air spring so as to control the air spring, for example through a leveling valve, to return the seat toward the home position in cases, for example, where the latch is latched and the load on the seat is varied so as to cause a change in seat elevation outside the predetermined range. For example, if an occupant leaves a seat while the seat is latched, the change in load on the seat results in upward movement of the seat because of a lesser load on the air spring or other seat height adjuster. When the seat raises beyond the upper limit of the predetermined range, deflation of the air spring commences to move the seat toward the central position. If the occupant again returns to the seat, the air spring will be compressed and the seat will move toward an elevation lower than the lower-most elevation of the predetermined range. In this case, inflation of the air spring commences to again return the seat toward the central position. Typically, the predetermined range of motion permitted before air spring inflation or deflation commences in response to variations in the load on the seat is slightly less than the range between the first upper extreme and second lower extreme of dampening motion permitted by the vibration damper.
The seat support in one form may include a base together with a seat supporting member adapted to carry the seat. In addition, first and second link members may be included to couple the seat supporting member to the base. The link members in effect form a parallelogram type linkage between the base and seat supporting member. Although sets of individual arms may be used for the first and second link members, in one specific illustrated form, they comprise respective upper and lower platform like elements. The first link member has a first end portion pivoted to the base for pivoting about a first pivot axis and a second end portion pivoted to the seat supporting member for pivoting about a second pivot axis. In addition, the second link member has a first end portion pivoted to the base for pivoting about a third pivot axis and a second end portion pivoted to the thereof, individually and collectively, such aspects being set forth above and also in the drawings and description which follows.